Means for removing sleet, &c., from electrical conductors.

Application filed September 4,1903.. Serial No. 171.386. (No model,)

To all whom it may concern:

Be it known that I, Elias E. Ries, a citizen of the United States, and a resident of New York, in the county of New York and State 5 of New York, have invented certain newand useful Means for Removing Sleet, &e., from Electrical Conductors, of which the following is a specification.

My invention has for its object the removal io of sleet, snow, ice, &c., from railway-tracks, more particularly from the contact-rails or supply-conductors that are usually employed on electric railways for supplying energy to the motors on the cars or trains traveling 15.thereon. Such contact-rails or supply-conductors are ordinarily located overhead in the form of trolley-wires, or underground in the case bf underground-conduit electric railways, or they are located along the road-bed 20 itself either between or at one or both sides of the track-rails, as in the case of third-rail el so trie-rail way systems, whether the same bo located on the surface or an elevated struetr res. In all such cases these contact or sup25 ply conductors being necessarily naked or uninsulated in order to permit of -electrical contact being made therewith by the trolleys, shoes, brushes, or other current-collecting de Hees with which the motor cars or trains 30 art equipped are more or less exposed to the ele nenis.

Ii the winter season it has been found in the operation of overhead - trolley, underground-conduit, and third-rail electric rail35 way 3 that the exposed contact-surfaces of the supjly-conductbrs when subjected to moisture at times v hen the surrounding atmosphere is even a few degrees below the freezing-point would cause a condensation of such 40 moisture thereon in the form of sleet, which interferes with the proper operation of the system It is also found that after a fall of rain, hail, or snow the moisture necessarily deposited upon the exposed line conductors 4.5 would freeze and incase the same with a crust of ice and dependent icicles, which prevent electrical contact of the shoes or other current-collectors with the supply-conductors, since such coating acts not only as a fairly 50 good insulator, but also serves to prevent mechanical contact of the collecting-shoes with the contact-rails, thus seriously interfering with the running of cars and in many cases tying up all traffic on the road.

It is my aim to maintain the efficiency of 55 an electric system, and particularly of an electric-railway system, by preventing the accumulation on such an exposed conductor of ice, sleet, snow, &c., or by removing the same after a partial accumulation of such 60 substance. I accomplish this result by heating the exposed conductor to a suitable temperature for melting and evaporating any rain, ice, snow, &c., which may fall or accumulate on the conductor. The desired ele- 65 ration of temperature is obtained bypassing through such conductor a suitable electric current. Any electrical system capable of raising the temperature of such an exposed conductor to the desired point at any hour 70 of day or night without interfering with the transmission of the regular electric current— such, for example, as the usual-motive or working current for propelling ears on aline of railway—should be so organized as to re- 75 move translating devices or motors, fed by the regular current from the influence of current designed to heat the exposed conductor.

The principal feature of my invention, therefore, is the provision of two paths or cir- 80 euits for current flowing in the system, one of these paths being the regular circuit through Which the working current flows, while the other path is a circuit through which a current of different character is passed, this 85 current being preferably of large heating capacity, usually an alternating current of low potential and large volume or amperage. As the exposed conductor forms part of the regular or working circuit, it will be evident that 90 in order to be heated up by another current of different character it should also form part of the circuit through which such heatingcurrent flows, and in my present system the two principal electric circuits have a common 95 conductor formed by the exposed conductor or third rail of the system, this exposed conductor usually constituting one side of each cireuitand permitting the simultaneous transmission therethrough of two currents of en- 100 tirely different characters, one of which is the regular or working current for supplying the translating devices or motors of the system, while the other is acurrentof entirely differ743,331 train having on the car a traveling heatingcircuit one side of which is a portion of the third rail included in the working circuit. 70 Fig. 4-is. a diagrammatic view similar to Fig. 1, illustrating a preferred construction for heating an exposed conductor or third rail, the entire heating-circuit in this view being divided into a plurality of sections each of 75 which has a separate source of current for economically heating the different sections. Fig. 5 is a plan of a modification of my invention, illustrating the manner in which three third rails may be connected and heat- 80 ing-current supplied thereto. Fig.-ti is a diagrammatic view illustrating third fails divided into sections heated by transformers connected in parallel and arranged in groups adapted to be energized separately. Fig. 7 85 is a detail illustrating diagrammatically means for supplying polyphase currents for heating exposed conductors. Fig. 8 is a detail illustrating automatic means for controlling the supply of the heating-current. Fig; 90 9 is a detail illustrating a^witch and a counter-electromotive-force device for controlling the current supplied to a heating-transformer. Fig. 10 is a cross-sectional detail of the traffic-rails and third rail of a third-rail system. 95 Fig. 11 is a detail illustrating a current-cMlecting shoe. for making contact with the third rail.

Similar characters designate like patti iu all the figures of the drawings. 100

My invention may be embodied in any elec-, trieal system in which it is desired to heat one of the conductors of an electric circuit, whether for the purpose of removing a light coating of dew, rain, sleet’, or snow or a heav- 105 ier coating of ice, &e., and it may be appliedto anj’ system in which such conductor is exposed to the elements,.although its principal use will be found to be in connection with the exposed or- working conductors of an no electric - railway system. It’is peculiarly adapted for use in third^:rail systems, because of the great surface ex posed to the elements by such a conductor and the consequent necessity for removing such a non-conducting and 115 contact-preventing medium as sleet or thick ice from the exposed working conductor.

In the case of a single-track system the third rail will of course be connected in a suitable heating-circuit, while at the same time eon- 120 stituting part of the regular working circuit;

> but as it is usual in third-rail installations to provide two or more tracks with corresponding working conductors or third rails I prefer to form a heating-circuit common to both 125 tracks by connecting the third rkils of the two tracks by cross-conductors and to provide at a point or or close to the track structure or line of way means for supplying a suitable electric current directly to the heating-circuit. 130

In Fig. 11 have illustrated a simple type of electrical system for supplying a working or motive current to the main cirbuit and for supplying, preferably simultaneously thereent character capable of heating the exposed conductor to the proper point for preventing or removing accumulations of sleet, snow, &c., without in any way interfering with the 5 transmission of the main electric current or with the proper operation of the translating devices supplied by such current.

In applying my invention to an electricrailway system I have found that it is feasiio ble to eliminate the traffic-rails as a factor from the heating-circuit, since these can be kept sufficiently cleared from deposits of sleet, ice, and snow by the regular traffic over the line, assisted in the case of a heavy fall of 15 snow by the ordinary mechanical appliances now generally used for clearing the road-bed of such accumulations. In accordance with my present invention, therefore,! utilize only the eontaet-rails in my heating circuit or cir20 cuits, and I do this ih such a manner as will permit of the transmissioh of the low-tension heating-currents preferably employed by me over the sarhe without in any wise interferfering with the simultaneous transmission 25 through the same of the regular propellingcurrents that are fed by said contact-conductors into the motor-circuits and are thenee returned through the traffic-rails. I am furthermore enabled by my invention to pro30 duce the necessary heating-currents with, comparatively speaking, a very small fraction of the total electrical energy that would be otherwise required. This latter feature, as will hereinafter more fully appear, I accom35 plish by cross-connecting the two supply-conductors of contact-rails of, say, a doubletrack' road at certain intervals, and thus subdividing the same into local heating-cirquitsof comparatively short lengths or sections.

In order to still further reduce the consumption of electrical energy—that is to say, id order to prevent the placing of too great a load upon the generators at the power station or stations of the line—I preferably provide 45 means, as will subsequently appear, for heating different sections or groups of sections successively instead of simultaneously. I also provide other novel features of construction and arrangement, as well as operation, 50 by means of which additional advantages and economies are gained and whereby mj' improved system may be readily and economically installed.

In the drawings accompanying this specifi55 eation and forming part of the present application, Figure 1 is a diagrammatic view illustrating three simple combinations of electrical devices for supplying a working current and a heating-current ‘separately or si60 multaneously to a main circuit and a heating-circuithavingaeommon conductor. Fig. 2 is a similar diagrammatic view illustrating the division of the rails of a third-rail system into sections of different widths, any one of 65 which sections may be heated independently of the others. Fig. 3 is a side elevation of a portion of a third-rail system, illustrating a

743.331 with, a current of different character, preferably of low potential, high amperage, and large heating capacity to an auxiliary or heating circuit. In this view 2 designates a source 5 of energy for supplying single or polyphase alternating current, this being the primary current on many electric railways, and 3 and 4 designate the usual mains or feed-wires. Three substations are also shown as supplied io with power from the main power-station, and at these substations suitable electrical apparatus is employed for supplying the different sections of the road with the working current and for also supplying heating-current 15 to the exposed working, conductors or third rails. The two tracks shown are designated by 5 and 6, respectively, and the third rails corresponding thereto are indicated at 7 and 8. In the construction shown in this view these to thitd rails are divided into sections of any desired length—say about two thousand feet— each section of the road preferably having the Opposite third rails thereof directly connected at at least one end thereof by a heavy »5 cross-conductor, such as the cable 9. In Fig.

the ends of these sections opposite the crossconductor 9 are connected in various ways to indicate the different means which may be readily used with existing types of third-rail 30 systems. In the first section of this view the system is so organized that the same source energy may supply the working current to the motive circuit and also the heating-current to the.auxiliary or heating circuit. In 35 this embodiment, however, which is intended toillustrate merely an emergency application of my invention, the current is turned off from the working circuit when it is desired to pass current through the heating-circuit. 40 This current is the usual direct or continuous current, delivered by a substation rotary converter 10, connected to the feed-wires 3 and 4, fed by the alternating-current generator 2. The wires 11 and 12, leading from 45 this converter, pass to the two-way switch 13 the arms of which cooperate with three terterminals,to which are connected three heavy bus-wires 14, 15, and 16, the first of which is connected to a cross-conductor or cable 17 for 50 bonding the ends of the wires of the two tracks nearest the substation, while the bus-wires 15 and 16 are connected directly to the third rails 7 and 8 of the first section. According to the positions of the switch 13, as indicated 55 in dotted and full lines, current is passed either through the two workingcircuits, which include the track-rails, or through an auxiliary¹ heating-circuit only, which includes the third rails of the working circuits, but ex60 eludes the track-rails thereof and the motors on the vehicles controlled by such worki n °· current.

In the second section (shown in Fig. 1) a substation rotary converter 18 is connected 65 to the feed-wires 3 and 4 by means of conductors 19 and 20, and the heavy conductors 21 and 22 of’the secondary circuit are connected, respectively, to the track-rails 5 and to the second section of the third rail 8, continuous current of relatively high tension be- 70 ing supplied by this converter to the working circuits .of the second section of the system._ In this second section the heating effect is not obtained by passing the whole of the direct current from the substation di- 75 rectly through the heating-circuit to the exclusion of the track-rails of the working circuit, as is done in the first section, but results from the use .of a rotary converter, which transforms a portion of the alternating line- 80 current into a direct current of lower potential, high amperage, and large heating capacity and feeds such low-tension current directly into the heating-circuit to the exclusion of the track-rails of the working circuit. 85 The primary of this rotary converter, which is designated by 23, is connected by suitable conductors to the main working circuit, connection being made herein to the conductors 19 and 20, and the secondary of the converter 90 is. connected by heavy conductors or buswires 24 and 25 to the second sections of the third rails 7 and 8, at the ends thereof opposite the eross-eohductor or bond-cable 9. The switch 26 is preferably placed in the main 95 circuit to said converter in order that current may be turned off from the converter, except at such times as it may be necessary to heat up the rails 7 and 8 to prevent or remove accumulation of sleet or other substance there- 100 on. This mode of heating the working conductors or third rails is preferable to that shown in the first section, as it is more economical and does not involve the turning off of the current from the working circuit or 10c circuits.

In the third section of Fig. 1 a substationconverter 27 is connected to the mains 3 and 4 by conductors 28 and 29 and is connected in the working circuit of the third section in no the same manner as thesnbstation-converte18. The heating-current in this case, however, is obtained from a static transformer 30, the primary of which is connected to the main .supply-circuit aud is controlled by a nr switch 31, while the secondary of the - trans- ⁴former is connected to the third rails 7 and 8 at the beginning of the third section by conductors 32 and 33. The efficiency of thi« mode of heating the third rails is approxt- 120 rnately the same as that of the second section.

It is desirable to subdivide the heating-current in all eases in order that the necessary heating effect may be obtained without making too sudden and heavy a demand on the 125 source of energy. This subdivision may be made jn various ways, one of which is illustrated in Fig. 2. Here the track-rails are designated by 5 and the working conductor or third rail by 7'. At different points in the 130 lengths of the track-rails and the tliird rail conductors, such as 35, 36, and 37and 38, 39, and 40, are connected thereto. Asouree of direct current, such as thegerwatorS'. is connected &

.'r/j K. O O that each forms a continuous conductor, ana ths two third rails are cross-bondsd._F as by means of heavy cables W, at suitable inter- 70 vals. These intervals need not-necessarily be be equal, and their lengths may bedetermined by the general nature--of the system at a given point or on a- given section, sections close to stations or containing upgrades, curves, or 75 switches, being preferably shorter than those on level stretches of the road in order that th© exposed conductor of such sections may be cleared quickly by the higher degree of heat automatically developed in these sections. So In the construction shown in Fig. 4 th© working circuit is supplied with direct currant from a substation rotary converter 10', which is fed with alternating current from an alternating generator 52 through feed-wires53 85 and 54. The secondary of this rotary converter is connected by means of conductor 55 to the rails o' and 6' of the two tracks and by means of conductor 56 to the cross bond or cable 9', that connects the two third rails 90 7' and 8'. At the ends thereof shown in the drawings the system has a closed trackcircuit through th© heavy bond-wire-17'. It will be observed that by this arrangement all th© track-rails are bonded or connected 95 together, so as to form one side of the working or railway circuit, while all th® third rails of the system are likewise electrically connected -together, so as to form the other side of the working circuit, as is now the ioo usual practice in third-rail systems. The alternating current transmitted overthe mains or feed-wires 53 and 54 is of high potential and in the working circuit of the railway system is transformed by the rotary eon- 105 •verter 10' into a direct current also having a relatively high potential. In the heatingcircuit, however, this alternating current is transformed into an alternating current of lower potential and high'amperage having no great (heating capacity by means of stepdown static transformers, such as 30\ of any suitable type, the primaries of these transformers being connected, as by means of conductors 57 and 58, to the feed-wires or mains 115 53 and 54, while the secondaries ar© connected directly to the exposed conductors or third rails 7' and 8'. Ob© of the most important features of my system with respect to economy of operation is the mode of supplying 12c heating-current to the heating-circuit,including the third rails. This I prefer to accomplish by feeding directly into such exposed conductors a transformed current of low potential and large heating capacity at such points 125 in tho system as will result in a minimum drop of potential owing to the relatively low resistance of each branch of the heating-circuit. Preferably each closed circuit formed by sections of the third rails 7' aucrS', con- 130 nected by cross-bonds 9’, is divided into at least two parallel branches in order to reduce the resistance, and the heating-current is fed directly into each branch—as, for example, to bus-bars 41 and 42, th© conductors 35,36,and 37 being connected to the former of these busbars,-while a conductor 43 may connect the end of the third rail 7' nearest the generator with 5 the bus-bar 42 through a normally open switch 44, which maybe closed when it is desired to permit the passage of the current through the third rail for heating it. The feeders 38, 39, and 40 are all normally conio nected in circuit with the bus-bar 42 through switches 45, 46, and 47. When it is desired to pass a heating-current through the third rail·?',the switch 44 is closed and the switches 45, 46, and 47 are all opened, thereby com15 polling the entire return-current to pass through the third rail and heat the same without passing through the feeders 38, 39, and 40. When this is to be done, the generator 2' may be speeded up to compensate for the so drop in potential due to the resistance of the long third rail. Traveling connection with the third rail is made through the usual current-collector or shoe 50, with one or more of which shoes each motor-car is customarily 35 provided.

In Fig. 3 I have illustrated a modification of my invention in which the track-rails are designated by 5 and the working conductor or third rail by 7. In this view the auxiliary 30 or heating circuit instead of being a -fixed section or block of the whole system is a traveling circuit, which is carried on and moves with the vehicle or train which is propelled by the working current. For the purpose of 35 converting the high-tension direct current of the working circuit into a current suitable for use in the heating-circuit a rotary converter, such as 23,. is placed on the vehicle and connected to receive current from the 40 working circuit through the current-collector or shoe 50' in the usual manner. A short local or heating circuit may be formed by connecting the secondary of this converter in circuit with said shoe and with another shoe 45 at the rear of the car or train, such as the shoe 50, from which a conductor 51 passes to the other terminal of the secondary of the converter, the shoe 50' being in circuit with oue of said terminals. A part of this local trav50 eling heating-circuit is of course common to the main working circuit, as in the systems previously described, and a very economical heating of the third rail is possible with this apparatus, as by its use the length of the con55 ductor to be heated at any one time is reduced, to a minimum. This short heating-circuit may be used to advantage on pilot or construction trains. For nearly all purposes, however, I prefer to- heat the exposed con.60 ductor or third rail substantially in the manner illustrated in Figs. 4, 5, and 6, in which three variations of the same general system are shown. In Fig. 4, 5' and 6' designate the down-track and up-track of a two-track 65 third-rail· system, and 7' and 8' represent the corresponding third rails. These third rails are preferably connected throughout, so '“43.3S1 by means of transformers (shown in Fig. 4) which are located at'approximately the centers of each section or block of the heatingcircuit. The courses followed by the two 5 branches of the current flowing from and to the secondary of each of these transformers are indicated clearly by. the arrows in Fig. 4. In most cases the length of each section or block of the heating-circuit may be, say, two io thousand feet on straight and level sections, so that each of the branch circuits fed by their common transformer will beabouta thousand feet in length ordinarily, which will result in a great saving as compared with such a section 15 of the heating circuit fed from One end there^no'^{i su}ridivided into parallel branches.

When the sections or blocks of the heatingcircuit are made shorter than this-—say onehalf or one-fourth the length of the ordinary 20 section, as will preferably be the case on upgrades, at starting-points, &c., for reasons that will hereinafter appear—it is apparent that the heating effect will be produced much more quickly than on a long section. The 25 extent to which it is necessary to heat these exposed conductors or third rails depends chiefly upon thetemperatureof thesurrounding atmosphere; but ordinarily it will not be necessary to raise the temperature of these 30 conductors more than 10° Fahrenheit, as sleet and ice are the principal substances to be removed from the exposed conductors, and these ordinarily form when the temperature is buta few degrees below the freezing-point. 35 A temperature ejevation of about 6° Fahrenheit will usually be sufficient, and this temperature elevation can be obtained by the expenditure of about thirty-five-horse power of electrical enegy per minute for a block 4P containing fou r thousand feetof the ordinary third rail, which weighs approximately one hundred pounds per yard and has a crosssectional area of about 9.8 square inches, with a conductivity approximately one-sev45 enth of that of a bar of copper of equal area, and can be maintained by about one-sixtieth part of the energy required to produce such an initial rise in temperature owing to the capacity of the rail for storing or retaining 50 the heat produced therein.

The greatest economy and the greatest practicable distribution of the extra load on the generator result from the use of such a system as that illustrated in Fig. 4, with the 55 lengths of the sections properly proportioned to the gradients, starting-points, &c., and from the application of heating-current to such sections separately or successively in . such a manner with regard to the degree of op elevation of temperature developed therein as to beat up the more important short sections first and in a relatively short time and the longer sections afterward somewhat more slowly, and such currents may with advan65 fage be applied intermittently or in regular succession instead of Continuously to the several sections, so as to still further reduce

I or distribute the load on the power station^It will be evident that by this method and by the proper utilization of the heat-storage ca- 70 pacify of the third rails themselves theextra or emergency current consumed in the heating-circuit is distributed over a longer time interval in that it is only used for short periods of time on each section and that the 75 sum of these periods represents not only a moderate expenditure of energy, but the requisite power for removing the sleet, &c., is developed without imposing too great or sudden a load on the generating or trans- 80 forming station, as might be the case if it were attempted to clear the entire line simultaneously and withinabrief interval of time— a procedure that I have found is as unnecessary as.it is uneconomical. 85

In Fig. 0 I have illustrated a modification of the invention adapted for use in connection with three main circuits or track-circuits, the exposed conductors or third rails only being shown, together with means for 90 supplying current thereto, as in other respects the system is substantially the same as that shown in Fig. 4. In this view, Fig. 5, the third rails 7^a and 8^a of the down-track and the up-track have between them a third rail 95 60, which is the working conductor of the circuit for a center track, such as is ordinarily used for express-trains on an elevated or underground third - rail system. These third rails are connected by cross-bonds 9^a to 100 form two closed parallel heating-circuits divided into corresponding closed sections. Current may be supplied to these sections in any suitable way before described; blit preferably a transformed alternating current of 105 low potential, high amperage, and large heating capacity is supplied to the various sections, the different branches of each section either having separate transformers connected directly in each branch, as at 30^a, or a sin- no gle transformer having a divided secondary being connected at the terminals of the secondary to the two outer rails and divided at the center of the secondary for connection to the center rail 60 to divide the current translated τ τ5 by the secondary between the two branches of the section.

In Fig. 6 I have illustrated another- modification in which the heating-circuit is divided into sections by the c'ross-bonds 9°, which 120 sections are fed with heating-current by transformers 30^c similar to those shown in Figs. 4 and 5. The primaries of these transformers instead of being connected in a single circuit are connected in groups m parallel in differ- 125 ent circuits, any one of which may be closed as desired, while the others remain open. In this view one wire 61 of each primary is connected to a common conductor 62, while the other wires of the primaries are connected in 130 pairs or groups to different conductors, the copductors 63 being connected to the condo c or 64, the conductors 65 to the conductor 66, and the conductors 67 to the conductor

743,331

68, each group being in parallel to reduce the resistance, -and- each of the conductors 64, 66, and 68 being separately connectible in circuit with th© source of energy, such as § the alternating generator 52^c, by means of a switch 70, movable onto any one of the contacts 71, 72, 73, and 74 as may be desired. I regard this method of connecting sections in circuit separately as the most economical, io because not only is the resistance of each section reduced to the minimum by the proper proportioning of the length of each section in accordance with the grade and other conditions and by the division of each section into 15 two parallel branches of equfcl resistance fed by a divided heating-circuit, but the extra load on the generator is kept down as much as possible by heating different groups of sections of the road at different times, and so thus distributing the extra demand for energy over a considerable period of time. To remove a thick coating of ice or other substance quickly, an alternating heating-current of relatively high frequency may be employed, 25 the “skin effect” of which will cause the surface of the rail to be heated first, which will result in the removal of practically all such coating before the body of the rail is heated up to any considerable extent.

In Fig. 7 I have illustrated at 75 a polyphase-generator of the “star” type having separate switches 76, 77, and 78 for three conductors 79, 80, and 81 leading therefrom, over which the currents of different phase may be 35 transmitted for heating different exposed conductors or third rails.

In Fig. 81 have illustrated how the primary of a heating-transformer, such as 30^d, may be automatically connected in circuit with 40 an alternating generator, such as.52^d, by means of an automatic.switch 82, operated in this case by a solenoid-magnet 83, controlled in any suitable manner and from any desired point.

In Fig. 91 have illustrated how the current from an alternating generator, such as 52®, may be passed either in series or divided and passed in parallel through the divided primary of a transformer, such as 30®, having a 50 switch 84 f.or changing the connections of the primary sections 85 and 86 of the transformer from series to parallel, or vice versa, an inductive resistance 87 being also connected in circuit with said switch and the 55 primary of the transformer. ' This arrangement of divided primary winding for the transformers is useful in places where it is desirable in emergencies to produce a more rapid clearing of the third-rail section (by 60 connecting the primary coils in parallel) than would be effected by the normal or “series” connection alone. It may also be employed for rapidly elevating the rail to the requisite initial temperature, after which the radiation 65 losses may be taken care of and the rail maintained at the desired temperature by restoring the series connection. It will be observed that the heavier secondary windings of the transformer are permanently connected across the third-rail sections, as I find this to be an 70 advantage even in seasons when the heating current or currents are not likely to be used, as in summer, &c.

The third rail of each track may of course be of any suitable construction and located 75in any well-known manner either at the side of the track or between the track-rails, as Illustrated in Fig. 10. It. will also be obvious that my invention may be applied equally well for the removal of sleet, &c., from over- 80 head wires and for the purpose of evaporating moisture from, and thus improving the insulation of, exposed conductors whether the same be used for electric-railway or other purposes. 85

Although the problem of removing ice, snow, &c., from exposed conductors, such as those of a third-rail system, may appear at first sight to call for the expenditure of such an amount of electrical energy as to inter- 90 fere with the proper operation of the system, it will be evident that when such removal is made in the manner described herein there will never be any abnormal load on the powerhouse due to the use of an abnormal amount 95 of current for heating purposes, because by dividing the system into sections of different lengths, heating those sections in the order of their importance either separately or in groups, varying the period during which the 10 heating-current is turned into the rails of a section, according as it is more or less impor tant to clean that section quickly or thoroughly, and by utilizing the heat-storage capacity of the rails, which admits of a rapid 105 heating of the section in a very short- time and a gradual radiation of the heat stored, which radiation will extend over a comparatively long period of time, my improved system may be employed with the expenditure no of a very small percentage of additional energy over that required for traction purposes and without materially increasing the load on the power-house.